This invention generally relates to a fluid flow indicator and, more particularly, to a compact apparatus capable of handling both high and low flow rates.
Fluid flow indicators have been known and used for many years. Conventional flow indicators have utilized a single ball which rotates in a track. The single ball tends to restrict the flow creating an undesirable pressure drop across the indicator, and the indicators are typically not sensitive to low flow rates, for example, less than 5 to 6 gallons per minute. The indicators of this type that are used in industrial applications involving high flow rates are usually made of a metal and are therefore relatively expensive. A further disadvantage to these metal flow indicators is that the indicator is visible from only a very limited angle.
Alternative flow indicators utilize a flutter-type device such as a vane, propeller or flexible fibers instead of a single ball. The flutter-type devices are more sensitive to low flows than the single ball devices but, at very low flow rates, the absence of flutter may erroneously indicate that no flow exists. Other disadvantages to the flutter-type devices are that they always involve a hinged member or pivot which can jam or wear, or they involve flexible fibers which can become immobilized due to tangled fibers or dried-on fluids and can operate in only a limited number of positions. Their use is therefore limited more to laboratory applications than high flow rate industrial situations. In addition the flutter-type devices often involve molding of custom parts.